The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Electric motors and generators are used for a multitude of tasks and commonly generate significant heat during operation. Typically, motors are constructed to have an ‘Open’ architecture or a ‘Totally Enclosed’ architecture. Generally, the architecture, i.e., the construction, of ‘Open’ motors comprise a motor housing, or enclosure, including a plurality of air flow ports or openings that allow air from the ambient exterior environment to be drawn into and exhausted from the motor enclosure to cool the electrical package of the machine (i.e., the rotor and stator). More particularly, motors having the ‘Open’ architecture include an electrical package wherein the rotor and stator each include radial vents that allow the cool air drawn in from the ambient exterior environment to flow through the radial vents, and hence, radially through the rotor and stator, to directly cool the electrical package.
Conversely, the motor housing of a ‘Totally Enclosed’ motor completely encloses the electrical package such that there is no free exchange of air from the ambient exterior environment into the motor housing. Additionally, motors having known ‘Totally Enclosed Fan Cooled’ motor architecture generally have no internal air circulation path for directly cooling the electrical package. Rather, the electrical packages of known totally enclosed motors are indirectly cooled by directing an air flow over and through heat exchanging vanes formed on the exterior of the motor housing. Since the electrical packages of known ‘Totally Enclosed Fan Cooled’ motors are not directly cooled by air, the rotors and stators do not include radial vents, such as those of motors having the typical ‘Open’ motor architecture.
As is known in the art of motors, the efficiency, and power output, i.e., power density, of a motor is directly affected by the temperature of the motor, e.g., the temperature of the electrical package, during operation of the motor. That is, motors are thermally limited such that the amount of power output by a motor is a function of how well the heat can be removed from the electrical package. Generally, a motor will operate more efficiently, and produce more power at cooler temperatures than the same motor operated at higher temperatures. Typically, ‘Open’ motor architecture provides better cooling than ‘Totally Enclosed’ motor architecture. Hence, ‘Open’ motors generally operate more efficiently and have a higher power density than ‘Totally Enclosed’ motors of substantially the same size.
Generally, an ‘Open’ motor can have 30% to 40% greater power density than most ‘Totally Enclosed’ motors of the substantially the same size. However, the air intake openings in the motor housing, and the intake of air, of ‘Open’ motors can allow debris to abrade, foul, contaminate, corrode, and/or damage the respective electrical package, thereby diminishing the performance of the motor. Known ‘Totally Enclosed’ motors are not subject to such damage by debris, but their efficiency and power output are constrained by their limited cooling ability and increased operating temperature.